Obturator for machinegun having laterally sliding breechblock

ABSTRACT

A consumable cartridge firing machinegun having a firing chamber obturator mounted in a longitudinally movable cartridgechambering rammer. The rammer has an aperture which receives a breechblock which slides laterally therein to engage a rearwardly projecting portion of the obturator for limiting obturator rearward movement when a cartridge is fired.

United States Patent Inventor John J. Scanlon, Jr. 56] References Cited Com UNITED STATES PATENTS Appl. No. 9,303

. 2,953,066 9/1960 Colby .1 89/186 med 3166 864 1/1965 5 1 89 6X Patented g 31, 197] can on /2 Assignee The United States of America as FOREIGN PATENTS represented by the Secretary of the Army 15,309 0/191 1 Great Britain 89/26 Primary Examiner-Benjamin A. Borchelt Assistant ExaminerStephen C. Bentley Attorneys-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and S. Dubroff OBTURATOR FOR MACHINEGUN HAVING LATERALLY SLIDING BREECHBLOCK 6 Clams 4 Drawmg Figs ABSTRACT: A consumable cartridge firing machinegun hav- U.S.Cl 89/26, ing a firing chamber obturator mounted in a longitudinally 89/47, 89/186 movable cartridge-chambering rammer. The rammer has an Int. Cl ..F41d 11/16, aperture which receives a breechblock which slides laterally F411 1 1/04 therein to engage a rearwardly projecting portion of the obtu- Field of Search 89/ 1.704, rator for limiting obturator rearward movement when a car- 1.705, 24, 26, 33 A, 47, 162, 167, 186; 42/14 tridge is fired.

I 1 1 1 I 1 1 1 1 1 l 1 1 I 1 PATENTED Ausal ran 3; 602.087

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INVENTOR BY-A M1 ATTORNEYS.

JOHN J. SCANLON JR.

PATENIEflAusal I971 3,602,087

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INVENTOR JOHN J. SCANLON JR.

ATTORNEYS.

I device which small caliber weapons must have if they are to be used successfully in conjunction with caseless or consumable cartridges.

In rapid-firing weapons having breechblocks which slide laterally into place behind a chambered cartridge, such as in the M--,73 machinegun, obturator mounting has presented problems, Since an obturator such as disclosed in the afore' mentioned patent must be longitudinally inserted behind a chambered round of ammunition, the .use of the breechblock as an obturator or obturator holder is obviated. The modificatiori'of an M-73 machinegun, for instance, to accommodate consumable cartridges, requires a novel obturator mounting arrangement which is the basis of this invention.

It is, therefore, an object of this invention to provide a machinegun capable of firing caseless or consumable ammunition.

It is a further objectof this invention to provide an obturator-mounting arrangement for use in weapons having laterally sliding-breechblocks.

Briefly stated, in my invention a machinegun cartridge rammer is used as an obturator holder. The rammer has a 1ongitudinal bore which extends between the rammer forward end and an aperture which .is formed therein transversely to the bore. .An obturator rearward end is slidably positioned in the bore'and extends slightly into the aperture area. This-obturator end is slightly tapered both inwardly and rearwardly for engaging a similarly shaped breechblock surface.

After the rammer has inserted a cartridge in the firing chamber, the breechblock is slid laterally into the rammer aperture. As the breechblock moves into the aperture a surface portion contacts the obturatortapered surface andcams it forwardly. The breechblock then locks itself in position in the aperture and prevents rearward obturator movement when the cartridge is fired.

Other objects, features and advantages of this invention may be seen by a perusal of the'following specification in-conjunction with the accompanying drawings in which:

FIG. I is an elevational view partially broken away and partially sectional, showing a machine gun embodying features of the invention.

FIG. 2 is a partial view similar to FIG. 1 with the gun parts in a firedposition.

FIG. 3 is an enlarged longitudinal sectional view of a certain mechanism in the FIG. 2 arrangement.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 2.

A conventional machine gun 11 (FIG. I), has an air-cooled barrel l2, coaxially connected to a cartridge firing chamber I3 which chamber is-sized to accommodate a caseless .or consumable round of ammunition. Obturator chamber 13A is coaxially aligned with and rearwardly of chamber 13 and receives obturator 27.

A caseless cartridge 14 is supported on longitudinally slotted feed tray I5. Feed pawls or grips 16, located within cover 17, position the cartridge in the slot and in axial alignment with firing chamber 13, by engaging feed link 55. The slot, not shown, permits rearward surface 19 of cartridge 14 to be in the operative path of-obturator forward surface 20, so that as the obturator moves forwardly, it contacts cartridge surface I7 and pushes the cartridge into firing chamber 13.

Rammer 21 is connected to conventional gas-operatedv machinegun linkage system 22A, partially shown, the linkage normally. retaining rammer2l in its rearwardmost position as shown in FIG. I. In combination with this linkage is trigger 22 which disengages the linkage when the trigger is rotated about pivot 60. The rammer is then moved forwardly under the urging of a conventional machinegun spring system, notshown.

An aperture 23 is formed in rammer 21 transversely to barrel longitudinal axis A-A. Aperture 23 is shaped to receive a breechblock 24 (FIGS. 1, 2) which is slidably mounted orthogonal or normal to barrel longitudinal axis A-A. Breechblock 24 is coupled to a portion of gun linkage 22A which moves the block laterally in response to a predetermined firing sequency. For example, after the rammer has moved forward into the firing position as shown in FIG. 2, the breechblock 24 is slid into a locking position in rammer aperture 23 as exemplified in FIG. 4. After the cartridge has been fired, the breechblock'is slid laterally .out of the apertive path of the rearwardly moving rammer.

Rammer 21 has a forward yoke 25 which has a stepped longitudinal bore 21A extending therethrough rearwardly of said rammer forward surface 24A. Bore 21A slidably receives a reduced boy portion 26 of obturator 27 and the yoke 25 is forwardly offset relative to its leg 25A to define a step in the rammer 21 to receive an enlarged end or flange 29 of obturator 27. Step 28 permits obturator rearward flange surface 30 to become flush with the rearward surface of yoke leg 25A when obturator 27 slides into its forward most position.

A firing pin 31, having a groove or reduced body portion 32 and a rearward end portion 33, is slidably positioned in a chamber 27A centrally located within the obturator. O-ring 34, sealingly engaging chamber wall 27A, is seated axially spaced split rings 35, 35.within groove 32. This Oring and split-ring arrangement is more fully described in my above mentioned patent and it should be referred to for detailed specification. Dowel or pin 48, engages a flange or firing pin end 33 to limit pin rearward movement while chamber shoulder 53 controls pin forward displacement.

Collar 36 is slid into place on obturator body portion 26 after that portion is inserted in the rammer bore. Obturator forward flange 37 is then threadably secured to a mating portion on the obturator. Between flange surface 38 and collar surface 39 is formed a groove or redudeddiameter for accommodating and O-ring and split-ringassembly, shown generally at 38A, which is similar to that 34, 35, 35 used in conjunction with the aforementioned firing pin assembly and discussed with specificity in my referenced patent. I

Breechblock 24 (FIG. 3) has a forward camming surface 40 which engages obturator rearward tapered-surface 41 to cam obturator 27 forwardly. A clearance space 42 is provided between rammer surface 24 and obturator collar surface 43. This clearance permits the obturator to move axially relative to the rammer to transmit developed firing forces directly through the obturator to breechblock surface 44 when the breechblock is locked in firing position.

Slidably positioned within the breechblock is an elongated member 49 which is rearwardly biased by spring 50. Member 49 has an end 51 which normally projects rearwardly of the breechblock with end 52 of member 49 being normally located within the breechblock. A conventional hammer 56, in response to a preselected firing sequency, contacts surface 51 of member 49 to initiate firing pin actuation.

Pivotally connected to the conventional machinegun linkage is firing pin striker or setback hammer 45. Surface 46 on striker 45 contacts firing pin forward surface 47 to urge the firing pin rearwardly after a cartridge has been fired and the rammer moves into its rearwardmost position.

The machinegun'operating cycle begins with rammer 21 being normally held in its rearwardmost position as shown in FIG. 1. Cover 17 is removed and one of a series of linked cartridges 14 is positioned on feed tray 15 partially in slot 18. Cover 17 is then replaced and pawls I6 maintain this cartridge position by engaging cartridge feed link 55. Rotation of trigger 22 by the gun operator will release the spring-loaded conventional gun linkage to urge rammer 21 forwardly. As the rammer moves forwardly, striker 45 moves downwardly out of the rammer path and obturator surface 20 contacts cartridge forward and intofiring chamber 13.

As the cartridge is being chambered, breechblock 24 is slid laterally toward its locking position within rammer aperture 23. As the breechblock enters aperture 23, breechblock forward surface 40 contacts obturator flange surface 41 which surface projects slightly into the aperture. This projection is due to frictional forces acting rearwardly on the obturator when its is inserted in chamber 13, thereby necessitating the breechblock camming action. Continued lateral movement of the breechblock cams the obturator forwardly and maintains an intimate contact between flange surface 30 and block surface 44. The maintenance of this intimate contact is desirable since even the slightest clearance between these surfaces would result in the breechblock having to absorb obturator inertial forces in addition to firing forces when a cartridge is fired. Such forces would place undesirable stresses on gun components to thereby accelerate their failure.

When the breechblock is locked in position, member 49 is aligned with firing pin end 33 and hammer 56 strikes member end 51. Member forward end 52 strikes firing pin end 33 which in turn moves the firing pin forward to fire the cartridge. Rearward passage of propellant gases is prevented by obturator 27, the mechanics of which is described with particularity in my above-referred-to patent.

Under the influence of propulsion gases generated by the fired cartridge, the conventional linkage assembly moves the breechblock laterally out of the rammer aperture. The rammer then moves rearwardly but before reaching its rearwardmost position, striker 45 contacts firing pin end 47 to reset the firing pin. As the rammer reaches its rearwardmost position feed pawls 16 position another cartridge on the feed tray and the cycle repeats until the operator releases the trigger.

i wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

I claim:

ll. In a machinegun having a barrel with a longitudinal axis, and

a caseless cartridge firing chamber coaxially aligned with said barrel, the combination with said gun of a chamber for slidably receiving an obturator, said obturator chamber being located rearwardly adjacent to said firing chamber and coaxial therewith,

a rammer for inserting a cartridge in said firing'chamber,

said rammer having a transverse aperture which receives a breechblock, said block being slidably mounted transversely to said axis, said rammer having a forwardmost yoke with a longitudinal bore extending therethrough,

an obturator with a rearwardly elongated reduced body portion slidably positioned in said rammer bore, said obturator having an enlarged rearward end for operatively contacting a forward surface portion of said breechblock whereby said breechblock limits obturator rearward movement when said cartridge is fired,

a firing pin longitudinally slidably retained within said obturator and aligned with said firing chamber,

. an elongated member retained within said breechblock and operatively aligned with said firing pin rearward end, means for biasing said member rearwardly of said breechblock,

means for urging said member into contact with said pin end in opposition to said biasing means, and

means including a striker for moving said firing pin rearwardly after said cartridge is fired.

2. The arrangement as defined in claim 1 wherein said obturator has a peripheral groove adjacent its forward end,

first ring sealing means seated in said groove for sealing said obturator chamber against rearward passage of combination gases,

a rearward flange on said obturator for limiting obturator forward movement,

a substantially centrally located firing pin chamber slidably receiving said firing pin, said firing pin chamber being defined by an obturator inner peripheral wall, said wall engaging a second ring sealing means positioned peripherally around a reduced body portion of said firing pin, and means for limiting firing pin axial movement.

3. The arrangement of claim 1 wherein said obturator has a removable forward flange and a rearward flange defining therebetween said reduced body portion,

a collar slidably positioned on said body portion,

ring sealing means located intermediate said forward flange and said collar, said sealing means having an O-ring positioned intermediate two axially spaced split rings, and

means for limiting firing pin axial movement.

4. The structure as defined in claim 3 wherein said obturator has a rearwardly facing surface portion which is inwardly and rearwardly tapered for operatively engaging a surface portion of said breechblock.

5. The structure in accordance with claim 4 in which said transversely mounted breechblock has a camming surface for engaging said obturator rearwardly facing surface portion.

6. The structure of claim 5 wherein at least one of said breechblock camming surface and said obturator rearwardly facing surface portion has a curvilinear cam surface. 

1. In a machinegun having a barrel with a longitudinal axis, and a caseless cartridge firing chamber coaxially aligned with said barrel, the combination with said gun of a chamber for slidably receiving an obturator, said obturator chamber being located rearwardly adjacent to said firing chamber and coaxial therewith, a rammer for inserting a cartridge in said firing chamber, said rammer having a transverse aperture which receives a breechblock, said block being slidably mounted transversely to said axis, said rammer having a forwardmost yoke with a longitudinal bore extending therethrough, an obturator with a rearwardly elongated reduced body portion slidably pOsitioned in said rammer bore, said obturator having an enlarged rearward end for operatively contacting a forward surface portion of said breechblock whereby said breechblock limits obturator rearward movement when said cartridge is fired, a firing pin longitudinally slidably retained within said obturator and aligned with said firing chamber, an elongated member retained within said breechblock and operatively aligned with said firing pin rearward end, means for biasing said member rearwardly of said breechblock, means for urging said member into contact with said pin end in opposition to said biasing means, and means including a striker for moving said firing pin rearwardly after said cartridge is fired.
 2. The arrangement as defined in claim 1 wherein said obturator has a peripheral groove adjacent its forward end, first ring sealing means seated in said groove for sealing said obturator chamber against rearward passage of combination gases, a rearward flange on said obturator for limiting obturator forward movement, a substantially centrally located firing pin chamber slidably receiving said firing pin, said firing pin chamber being defined by an obturator inner peripheral wall, said wall engaging a second ring sealing means positioned peripherally around a reduced body portion of said firing pin, and means for limiting firing pin axial movement.
 3. The arrangement of claim 1 wherein said obturator has a removable forward flange and a rearward flange defining therebetween said reduced body portion, a collar slidably positioned on said body portion, ring sealing means located intermediate said forward flange and said collar, said sealing means having an O-ring positioned intermediate two axially spaced split rings, and means for limiting firing pin axial movement.
 4. The structure as defined in claim 3 wherein said obturator has a rearwardly facing surface portion which is inwardly and rearwardly tapered for operatively engaging a surface portion of said breechblock.
 5. The structure in accordance with claim 4 in which said transversely mounted breechblock has a camming surface for engaging said obturator rearwardly facing surface portion.
 6. The structure of claim 5 wherein at least one of said breechblock camming surface and said obturator rearwardly facing surface portion has a curvilinear cam surface. 